In the co-pending patent application Ser. No. 748,982, filed Dec. 9, 1976 in the names of Joseph D. Heaps and Obert N. Tufte, entitled "Method for Dip-Coating Ceramic with Molten Silicon" and assigned to the same assignee as the present invention, there is described a method for dip-coating ceramic bodies or sheets with molten silicon to prepare large area, thin sheets of large grain polycrystalline silicon for use in solar panels and the like. In that method the side of the ceramic sheet or the area to be coated with silicon is first carbonized since molten silicon does not otherwise wet ceramic. When electrically insulating ceramic substrates of that nature are coated with silicon by that method or other methods that bring the ceramic sheet into contact with the molten silicon, electrical contact can only be made conveniently to the exposed or top surface of the large area silicon coating. If the silicon coating is used for fabricating two-layer devices, such as solar cells, the bottom or interface layer is inaccessible to making electrical contact without sacrificing a portion of the top surface area for cutting or etching through the layer to reach the bottom layer thereby making the bottom layer accessible to electrical contacting. In order to minimize the solar cell's internal series resistance, good contact must be made to this bottom layer without utilizing any of the solar cell's top surface and thereby waste the effective area upon which solar radiation falls.
In the present invention it was discovered that by providing narrow slits or small holes in the ceramic substrate that upon coating one side of the ceramic substrate with molten silicon, the molten silicon will wick through the slits or holes to provide electrical contact points to the bottom layer of the silicon at the uncoated side of the substrate. Although the concise term "wick through" is used throughout the specification and claims, a more precise explanation of the action of the molten silicon might be that the silicon will be drawn by surface tension through the slits or holes.